Hypothesis / aims of study
This is the first study examining predictors of failure following direct-implant Sacral Neuromodulation (SNM) for Faecal Incontinence (FI), and the first to investigate the impact of adverse childhood experiences (ACE) on SNM outcomes.
SNM is an established treatment for FI. Following standardization of the implantation technique in 2017(1), high test-phase success-rates have supported increasing use of direct-implant SNM to reduce resource utilization.
Psychosocial factors, including ACE, are increasingly recognized as modifiers of outcomes in chronic disease, with higher ACE-Q scores being associated with an increased risk of early treatment attrition(3), however, the role in SNM outcome remains unexplored. A proportion of patients discontinue SNM-therapy and undergo device explantation, but predictors of treatment failure remain poorly defined. The direct-implant SNM approach enables evaluation of outcomes without the selection bias inherent to staged testing.
We hypothesized that clinical factors and coexisting conditions, including urinary symptoms and psychosocial factors such as ACE, are associated with outcome and subsequent explantation. The aim of this study was to determine the explantation rate following direct-implant SNM for FI between 2017 and 2023 and to identify patient characteristics and baseline factors associated with explantation.
Study design, materials and methods
In this retrospective cohort study, prospectively registered data from the Norwegian Registry of Anal Incontinence was analyzed. Between 2017 and 2023, 179 patients underwent SNM at a tertiary centre in Norway, of whom 95 received direct-implant SNM for FI. Revision procedures (n=84) were excluded from further analysis. Patients were stratified according to explantation status. Demographic and clinical variables were compared, including FI severity (St Mark´s score, 0-24), urinary incontinence (UI) severity (ICIQ-UI SF, 0-21) and adverse childhood experiences severity score (ACE-Q, 0-10).
Between-group comparisons were performed using non-parametric tests. Logistic regression analyses were conducted to identify factors associated with explantation. Written informed consent was obtained from all patients, and the study was approved by the Norwegian Data Protection Authority (PVO)
Results
Of 95 eligible patients, 11 underwent explantation. Among these, 2 were excluded due to death (n=1) and lack of consent (n=1). Of the 84 patients with ongoing treatment, 21 patients were excluded, leaving 72 patients in the final analysis (9 explanted, 63 ongoing), corresponding to an explantation rate of 12%.
The primary reason for explantation was lack of efficacy (5/9, 56%), followed by adverse events (painful stimulation; 3/9, 33%) and need for MRI (1/9, 11%).
There were no significant differences between groups in age, sex, body mass index, or baseline St Mark’s score. The explanted group had a higher mean (SD) higher ICIQ-UI SF score (14.8 ± 6.5 vs 7.6 ± 6.3; p=0.003) and higher ACE-Q score (2.3 ± 3.0 vs 1.0 ± 1.9; p=0.046).
On logistic regression, each one-point increase in ICIQ-UI SF score was associated with increased odds of explantation (OR 1.23; p=0.009). Patients (27/72, 38%) with ACE-Q>0 demonstrated a smaller mean reduction in St Mark’s score (2.8, 95% CI 0.26–5.3; p=0.031).
Interpretation of results
The explantation rate was low and comparable to outcomes with staged approaches, supporting the use of direct-implant SNM for FI. Patients who discontinued therapy demonstrated higher baseline UI severity and greater burden of ACE. Notably, the presence of ACE was associated with reduced improvement in St Mark´s score, suggesting a previously unrecognized factor influencing outcome.
These findings highlight the importance of assessing broader patient characteristics, beyond FI severity alone, when evaluating candidates for SNM. However, the results should be interpreted with caution given the limited number of explanted patients.